During the acute inflammatory response, which of the following is the primary mechanism responsible for the increased vascular permeability that leads to edema?

The correct answer to the question "During the acute inflammatory response, which of the following is the primary mechanism responsible for the increased vascular permeability that leads to edema?" is Option B: Endothelial cell contraction.

The other options — A) Vasoconstriction of arterioles, C) Increased lymphatic drainage, D) Decreased hydrostatic pressure — are incorrect for this USMLE Exam Prep question. As explained above: Endothelial cell contraction, primarily induced by mediators like histamine and bradykinin, increases gaps between endothelial cells. This allows plasma proteins and fluid to leak into the interstiti…